1. Field of the Invention
The present invention relates generally to stump grinders and, more particularly, to a stump grinder having an automatic reversing feed assembly.
2. Description of the Related Art
It is known to provide a stump grinder for grinding undesirable tree stumps. Typically, a stump grinder includes a frame, an engine or other drive mechanism such as a belt tension engagement mounted to the frame, a cutting assembly having a boom pivotally secured to the frame, and a rotatable cutting wheel operatively supported by the boom and driven by the engine. The stump grinder also includes an actuating assembly to move the stump grinder and/or cutting assembly relative to the stump and a control system to control the direction and rate of movement of the actuating assembly. Such actuating assemblies are typically hydraulic in nature, but may also be pneumatic, electronic, or mechanical.
During removal of a tree stump from a landscape, an operator directs the actuating assembly to move the cutting assembly to engage a portion of the stump through the control system. As the cutting assembly engages the stump, the operator will typically laterally advance or feed the rotatable cutting wheel across an upper surface of the stump, grinding away a top portion of the stump. This could also be done vertically, diagonally, or forward and back. Upon completion of a lateral pass across the stump, the operator will adjust the cutting assembly to engage the top surface of the stump and once again direct the rotatable cutting wheel across the upper surface of the stump in a lateral motion. This process is repeated until the stump is completely ground to an acceptable depth, which is typically below a grade of the landscape. Thus, the manner in which the operator directs the actuating assembly through the control system will directly affect the rate at which the cutting assembly will grind a stump.
Accordingly, the productivity of the stump grinder is dependent on the operator to maintain an appropriate rate of speed and depth engagement between the cutting assembly and the stump. Exerting too much force against the stump will slow the rotation of the cutting assembly and overwork the engine, which may result in engine stall or part failure. When the engine stalls or a part fails, the stump grinder may become plugged or otherwise inoperable. As a result, the stump grinder has to be unplugged or serviced, the engine restarted, and then redirected at the stump. This is a relatively time consuming and labor intensive process, resulting in higher costs, which is undesired. Conversely, exerting too little force against the stump will under-work the engine, resulting in a more time consuming process and a loss of productivity, resulting in higher costs.
Conventionally, maintaining a balance between overworking and under-working the engine is based on an operator's sensory perception of a working stump grinder. By way of example, an operator makes a feed rate adjustment based on engine sound or vibration felt in the controls. However, an operator's sensory perception is highly subjective relative to one's skill/experience, ambient conditions, and stump condition, thus, subject to a loss of maximum efficiency.
In an effort to maintain optimum output of a stump grinder, U.S. Pat. No. 6,014,996 to Egging et al. discloses a control system for stump cutters. In that patent, a stump grinding machine has a sensor for sensing a speed of rotation of an engine and a control for controlling movement of a stump cutter toward a stump based on the rotational speed of the engine. Specifically, the rate at which the stump cutter moves toward a stump in increased, decreased, or halted based on engine speed. As the engine becomes overworked, the stump cutter stops advancing or reduces its advancement speed through the stump until the engine speed increases.
One disadvantage of the above stump grinding machine is that the advancement of the stump cutter toward a stump is continued, albeit at a slower rate, when the engine speed begins to decrease. Despite the slower rate, an excessive load may continue to be placed on the engine, which can result in engine stall or component failure. Further, this type of stump grinder also suffers from the disadvantage of delaying engine recovery time since the cutter is still in contact with the stump although at a lower feed rate. Maintaining stump contact when engine speed is decreased may result in engine stall or part failure. Therefore, there is a need in the art to provide a stump grinder that overcomes the above disadvantages by reversing the feed direction of the cutting assembly relative to a stump in response to an excessive load.